1. Field of the Invention
The present invention relates to a substrate treatment apparatus for performing a cleaning process to clean the periphery of a substrate. Examples of the substrate to be cleaned include semiconductor wafers, substrates for liquid crystal display devices, substrates for plasma display devices, substrates for FED (Field Emission Display) devices, substrates for optical disks, substrates for magnetic disks, substrates for magneto-optical disks and substrates for photo masks.
2. Description of Related Art
In semiconductor device production processes, contamination of the periphery of a semiconductor wafer often significantly influences the treatment quality of the semiconductor wafer. In a so-called batch treatment process, for example, a plurality of semiconductor wafers are immersed in a vertical orientation in a treatment liquid. Therefore, if contaminants are present on the peripheries of the semiconductor wafers, the contaminants float in the treatment liquid and adhere onto device formation regions of front surfaces of the semiconductor wafers, thereby contaminating the device formation regions.
This leads to a recent increasing demand for techniques for cleaning the peripheries of semiconductor wafers and other types of substrates.
Japanese Unexamined Patent Publication No. 2003-197592, for example, proposes a prior-art apparatus for cleaning the periphery of a substrate. The apparatus includes a turntable which holds and rotates the substrate, and a cylindrical brush for cleaning a peripheral surface of the substrate. Before the start of a cleaning process, the brush is located in a standby position apart from the turntable. Upon the start of the cleaning process, the brush is moved from the standby position into abutment against the peripheral surface of the substrate held on the turntable. Then, the turntable is rotated with the substrate held thereon and with a circumferential surface of the brush kept in abutment against the peripheral surface of the substrate. Thus, the peripheral surface of the substrate is kept in sliding contact with the brush, and thereby cleaned by the brush.
However, the proposed apparatus does not necessarily ensure that the brush is kept in abutment against the peripheral surface of the substrate during the cleaning process. If the brush happens to be offset from a normal position or detached from a brush holding member, the brush will be brought out of abutment against the peripheral surface of the substrate, making it impossible to properly clean the peripheral surface (periphery) of the substrate.